give access to school library

I have a school who wants to buy on demand access to a video.

they said:
"We have about 80 students at any one time. Streaming the video concurrently, probably less than 5. If you were using a user licence model probably realistically we could go as low as 3. Or maybe we could try access with a certain amount of licenses then count lockouts and maybe add more?"

So I am used to selling single access to single user.....any ideas how I could set this up?